The Internal Revenue Service is planning to ask more than four million of the working poor who now claim a special tax credit to provide the most exhaustive proof of eligibility ever demanded of any class of taxpayers.

The I.R.S., trying to prevent errors and cheating, says it needs greater proof of eligibility months before people claim the credit on their tax returns because its efforts to find errors through audits after the fact have not worked. Treasury officials estimate that $6.5 billion to $10 billion is lost to improper payments each year.

But some tax experts criticize the higher burden of proof as unfair and a wasteful allocation of scarce I.R.S. enforcement dollars. They say that corporations, business owners, investors and partnerships deprive the government of many times what the working poor ever could — through both illegal means and legal shelters — yet these taxpayers face no demands to prove the validity of their claims in advance with certified records and sworn affidavits.

To build its case for war with Iraq, the Bush administration argued that Saddam Hussein had weapons of mass destruction, but some officials now privately acknowledge the White House had another reason for war — a global show of American power and democracy.

Officials inside government and advisers outside told ABCNEWS the administration emphasized the danger of Saddam's weapons to gain the legal justification for war from the United Nations and to stress the danger at home to Americans.

"We were not lying," said one official. "But it was just a matter of emphasis."